The present invention relates to liposuction apparatus, particularly to liposuction cannula shafts mounted via a swan neck to a handpiece, and more particularly to long, highly flexible metal or plastic cannula shafts which can be flexed to a semi-circular configuration and return to their original shape.
Liposuction, which literally means "fat suction", is a technique that pulls fat out of the body by means of teasing, pulling, scraping or suction. It can be used to reduce the volume of fat in many regions of the body, but is particularly effective in areas such as thighs and abdomen which contain genetically determined fat not responsive to diet or exercise. Liposuction is currently an established modality in cosmetic surgery, performed by surgeons as an elective operation, and is one of the most common procedures in medicine.
Traditional and ultrasonic liposuction cannulas usually are relatively rigid. The relative rigidity has its advantages and disadvantages. Advantages of relative rigidity include control, ease of manufacture and propagation of ultrasonic energy. Disadvantages of the rigidity include the fact that most areas of the human body are curviform and that the combination of straightness and rigidity places undesirable forces on the tissues adjacent to the cannula tips and tissues of the entrance wounds while the cannula is inserted in the patient. An article entitled "Reinforced Swan-Neck, Flexible Shaft, Beveled Liposuction Cannulas", P. J. Weber et al, The American Journal of Cosmetic Surgery, Vol. 16, No. 1, 1999, 41-47, described the use of a stainless steel shaft system with a reinforced swan neck for shaft diameters between 2.0 and 3.5 mm and drew comparisons with the prior art. Such a reinforced swan neck/shaft system is also described and claimed in above referenced copending Application Ser. No. 09/203,413 for use with sonic, ultrasonic and cooling systems. This system allows the cannula point of entry to act as a fulcrum (with an optional interposed insert) in concert with the surgeon's guiding hand to deflect cannulas with long flexible shafts and highly reinforced swan necks. The cannula tip is preferably highly beveled with an adjacent set of three openings. The system easily penetrates fibrous fat and may reach fat deposits relatively distant from the entrance wounds. The highly flexible, reinforced swan neck cannula shafts are intended to move in an easily controllable manner within the subcutaneous tissue below the dermal envelope in an arciform fashion. Benefits include a reduced need to move a patient's body position intraoperatively. A Teflon entrance wound insert (or anti-friction means), also described and claimed in copending Application Ser. No. 09/203,413, provides for reduced friction and tissue trauma at the dermal-epidermal level. The surgeon may require time to become proficient at maximizing the usage of novel cannula motions that occur as a result of using the cannula entrance point as a fulcrum and redirecting the distal shaft and tip of the cannula with an opposing hand. The novel motions arise from the minimally to highly arced possible cannula paths.
Many innovative cannula types and designs have been described and manufactured. Over time, the most commonly used variations have become the basis of traditional liposuction cannula design. Cannula designs may be categorized according to tip, aperture, shaft, handle, alloy and customization features. The cannula system described and claimed in copending Application Ser. No. 09/203,413 contains a unique combination of modifications and innovations not previously known. That 2.5-3.5 mm diameter metal shaft system was originally conceived to address the needs of ballerinas, fashion models, professional cheerleaders and the like's concerns about delicate fat removal with a minimum of cannula entrance wounds. Other issues that fostered a need for the cannula system included body curvature considerations and the need for intraoperative patient movement and positioning on the table. Previous attempts to address similar needs included the use of various long, rigid but slightly curved cannulas.
Many cannula tip designs are currently available. Each design has its positive and negative dynamics or attributes under varying conditions of usage. Liposuction cannula design dynamics have been summarized in the above referenced article by P. J. Weber et al. The tri-port bevel tip of copending Application Ser. No. 09/203,413 has been found to penetrate the fibrous fat with relative ease in combination with the systems herein described. Cannula passage in even the fibrous environment of previously suctioned patients appears facilitated. The tri-port bevel tip combination, although a very aggressive fat removing design, has yielded as little bleeding as we have seen with any other cannula tip design. Precise control over the aggressive action of multiple tip opening cannulas is recommended and may be gained by reducing the suction pump vacuum level to a suggested level of -12 Torr. The reinforced swan neck cannula should be moved slowly at first through the patient's tissues until the surgeon develops the necessary skills to consistently guide the cannulae to the appropriate target. Slow passage of these cannulae will usually provide aggressive liposuction and should be continuously monitored visually through the clear suction tubing and by target site palpation.
Swan neck modifications have been used in the past to aid the surgeon in directing the movement and placement of the cannula in close areas. Nonetheless, the forces customarily generated by the surgeon's arm during the course of surgery have been known to cause premature breakage in previous swan neck design junctions. Problems with earlier swan necks have included localized metal weakness, fracture, failure, undesired "bendability" and awkwardness. More positively, the reinforced swan neck of copending Application Ser. No. 09/203,413 provides a previously unattainable example that can now more fully demonstrate the many benefits of swan neck systems. Swan neck formations are especially helpful in combination with longer cannula shafts since traditional cannula linearity, length and rigidity may contribute to increase the probability that the surgeon's hand or cannula handle will bump or strike a patient's protuberance or convexity. Without swan neck modifications, the cumbersome length and rigidity of designs of previous cannulas caused surgeons to place additional stress on their own arms and the patient's tissues to guide the cannula shaft and handle in a workable fashion. In the above referenced 2.5-3.5 mm metal shaft cannula system, the swan necks have been specially and grossly reinforced. This reinforcement provides the needed additional stability at the handle/shaft junction to help a surgeon increase leverage on the cannula shaft and thus make use of the cannula entrance point as a fulcrum. Increased shaft leverage, in turn, allows the tip of the cannula to move in both traditionally expected and novel directions. To the surgeon who is not accustomed to using the new cannulas, this change and apparent unpredictability of tip movement may be alarming. Fortunately, with practice, tip motion can be perfected and the benefits of the new cannulas will become apparent.
Factors affecting a surgeon's selection of shaft length and character may be numerous. These factors may include the following: ease of tip location detection with shorter cannulas, concerns of increased handle/shaft junction breakage with increased length secondary to length-induced leverage, the secondary need for increased shaft diameter to increase strength (durability) when a longer cannula is desired, the advantage of minimizing the number of holes by using longer cannula. The reinforced swan neck allows for an increased range of workable cannula lengths for a variety of metal shaft diameters. These attributes, together with the special tip bevel, allow controllable tissue penetration with novel motions that should reduce the number of entrance incisions, hasten the procedure, reduce the need for patient repositioning. These benefits have been attained without apparent increased bleeding or complications. The use of high memory, extended length cannulas allows for movements and attributes heretofore considered problematic. For example, unique approaches to "hard-to-reach" areas, as well as decreasing the number of entry point openings, may modify a surgeon's repertoire.
Along with the tip modification and swan neck modification changes, shaft specification alterations have been made. The longer stainless steel shafts have been successfully used in all of our liposuctions performed numerous times. Stainless steel shafts in this cannula system are 2.0, 2.5, 3.0 and 3.5 mm in diameter. Currently available stainless steel tubing does not provide the flexibility or memory needed for proper function for shaft diameters exceeding 3.5 mm. However, certain alloys may enable an increase in diameter to about 5 mm.
Although shaft diameters between 2.0 and 3.5 mm provide surprisingly efficient and aggressive liposuction, many surgeons require cannula shaft diameters exceeding 4 mm to address obese patients and larger liposuction cases. However, metal cannulas with long shafts exceeding 3.5 mm in diameter of stainless steel were found on extensive testing to not possess the desirable qualities of a wide range of flexibility in combination with proper memory. The range for metal shafts is up to about 5.0 mm, preferably about 3.5 mm.
The present invention provides a new system using plastic cannula shafts with internal memory metal support wires which satisfies the need for cannula shafts having diameters of over 3.5 mm and up to 6-7 mm diameters. This plastic/support wire system has been tested successfully. The invention allows controlled rigidity of the plastic shafts and the cannulas can be bent into a semi-circle without breaking and yet still return to the original shape due to the internal metal support wire which provides the memory for the plastic shafts. The metal support wire decreases in thickness toward the distal end and may be covered with a Teflon coating to prevent excess load heating during autoclave sterilization of the plastic shaft. Also, the reinforced swan neck is provided with a disconnect which enables ready change of shafts of different diameters. Thus, the plastic cannula shaft system of the present invention, along with the above referenced metal cannula shaft system, provides a surgeon with the tools necessary to perform the complete spectrum of various liposuction procedures.